A Closer Look At SpaceX’s Falcon Heavy
The Falcon Heavy is not only one of the most powerful rockets in the world but also one of the most unique. After a few successful initial launches, there was a multi-year period without any missions. Thankfully, recently this came to an end and now the rocket is in the middle of its busiest year ever. All this being said, the design and development of this launch vehicle were far from easy.
Unfortunately, it’s not as simple as strapping two extra Falcon boosters to the side of a Falcon 9. In reality, an immense amount of work and innovation went into creating this system that still isn’t perfect. With the next launch scheduled just over a month away in July, SpaceX is already preparing for lift-off.
Here I will go more in-depth into the engineering behind this rocket, the work still being done to improve it, what to expect in the coming weeks, and more.
In-Depth Design
From the start, Falcon Heavy was built on the proven, highly reliable design of the Falcon 9. Falcon Heavy’s first-stage comprises three Falcon 9 first stages with enhancements provided to strengthen the cores. Furthermore, Falcon Heavy utilizes the same second stage and same payload fairing as flown on Falcon 9, fully benefitting from the flight heritage provided by Falcon 9 flights. This commonality has also minimized infrastructure unique to the vehicle.
Each booster has nine Merlin 1D (M1D) engines. Each of the 27 first-stage engines produces 190,000 lbf of thrust at sea level, for a total of 5,130,000 lbf of thrust at liftoff. The two side boosters are connected to the center core at the base engine mount and at the forward end of the LOX tank on the center core. In this case, the fundamental purpose of the side cores is to apply axial force to the center core during ascent and increase the impulse delivered to second stage before stage separation. The timing of the shutdown for the Falcon Heavy side cores can be tailored for each mission to ensure that the proper impulse is delivered. Two pneumatic pusher separation mechanisms connect the forward ends of each side core to the center core. They maintain the connection during ascent and then actively jettison the side cores following side core shutdown.
With nine engines in each first-stage core, Falcon Heavy has propulsion redundancy – unlike any other heavy-lift launch system. The launch vehicle monitors each engine individually during ascent and can, if necessary, preemptively command off-nominal engines, provided the minimum injection success criteria are achievable with the remaining engines. This engine-out reliability provides propulsion redundancy throughout first-stage ascent – a feature unique to Falcon launch vehicles. Structurally the center core consists of thicker tank walls and carries the booster separation system.
The first-stage propellant tank walls of the Falcon vehicles are made from an aluminum lithium alloy. Tanks are manufactured using friction stir welding—one of the strongest and most reliable welding techniques available. A common dome separates the LOX and RP-1 tanks, and a double-wall transfer tube carries LOX through the center of the RP-1 tank to the engine section. Four grid fins near the top of the first stage along with four deployable legs at the base are nominally flown to support recovery operations. While this is the standard, we have seen a few different variations in just the last couple of missions. For example early this year during the USSF-67 mission, Falcon Heavy launched with the center core in an expendable configuration (No grid fins or landing gear). This increased the available performance of the booster which was necessary for the payload.
In addition, the most recent mission last month saw the first ever fully expendable Falcon Heavy launch where all three of the boosters took off without any grid fins or landing gear. This variability allows the rocket to adapt depending on the mission requirements.
The Falcon Heavy design and development turned out to be a lot harder than SpaceX had expected. Specifically, the integration and structural challenges of combining three Falcon 9 cores were much more difficult than expected. Back in July 2017, Elon Musk was quoted saying, “It actually ended up being way harder to do Falcon Heavy than we thought. … We were pretty naive about that”.
New Challenges
While the Falcon Heavy has performed very well in the past few years, SpaceX is trying to improve the rocket and any of its shortcomings. Still, to date, SpaceX has struggled to successfully land the center core of the booster. So far there have been 6 total missions with the three most recent all featuring an expendable center core that was purposely destroyed. However, the first three missions all saw the center booster core lost. On the first mission, the center core struck the ocean after two of its engines cut out. On the second Falcon Heavy mission, the center core managed to land but subsequently fell over and was destroyed. During the third mission, the booster also impacted the ocean similar to the first attempt. While this may seem concerning, in reality, all three of these attempts occurred between 2018 and 2019.
By now SpaceX has gotten significantly more consistent on both droneship and ground landings with multiple or single boosters. If it weren’t for the center core being purposely expended on the last three missions, it’s very likely we would have seen three boosters touching down.
The other challenges have to do with the rocket’s history and the long break without a mission. In June 2019, Falcon Heavy lifted off one more time with a military satellite on top for the United States Department of Defense. Between June 2019 and November 2022, there was not a single Falcon Heavy mission. The rocket had seemingly disappeared after a very impressive start.
One of the main reasons for this was the success of the Falcon 9. After developing the Falcon 9 SpaceX worked to improve and increase the launch vehicle’s performance. At the same time, when developing Falcon Heavy, the company wasn’t exactly sure what the Falcon 9 would be capable of. SpaceX was so successful that the Falcon 9 became a lot more powerful than expected. So powerful that a lot of planned missions for Falcon Heavy ended up getting moved to the Falcon 9 which was cheaper. In this case, different commercial companies needing a ride to low Earth orbit for example simply didn’t require the significant payload capacity that the Falcon Heavy offered. Instead, they opted for a less expensive ride on the Falcon 9. SpaceX sells Falcon 9 missions for close to $67 million, whereas a standard Heavy flight goes for around $97 million.
Another reason had to do with a lack of demand. The area where Falcon Heavy really shines is heavy satellites meant for distant orbits. This specific mission profile narrows down the options significantly and mostly includes military launches. Between 2019 and 2022, the need for such a powerful rocket was simply limited. Delays also caused this stretch of no launches to continue. Several planned Falcon Heavy launches were pushed back due to issues with their satellites. USSF-44 for example was originally supposed to lift off in late 2020, but payload problems scuttled that plan. This launch only recently took place on the rocket’s long awaited return. In addition, there are a few competitors that offer comparable capabilities including Arianespace’s Ariane 5 and United Launch Alliance’s Delta IV Heavy, which both launched within that time period.
Lastly, around the time of Falcon Heavy development and lack of launches, SpaceX was ramping up work on Starship. It seems as if the company had a lot of plans but was unsure exactly what each project would be capable of and when. This packed full schedule and various options likely contributed to the lack of launches for various other reasons as well. Even though all this information sounds somewhat grim for the company and rocket, in the grand scheme of things they have had a lot of success with Falcon Heavy and made a notable amount of money. For example, a year after the successful demo flight, SpaceX had signed five commercial contracts worth US$500–750 million, meaning that it had managed to cover the development cost of the rocket. SpaceX was also awarded 40% of the launches in Phase 2 of the National Security Space Launch (NSSL) contracts, which includes several launches and a vertical integration facility and development of a larger fairing, from 2024-2027. Now in early 2023, the rocket is in the middle of its busiest year ever.
Currently, there are at least three more missions scheduled this year and 5 scheduled for 2024. The rocket went from not launching for years to averaging a mission every two months or so. With the Falcon 9 and Falcon Heavy launch vehicles, SpaceX is trying to offer a full spectrum of medium- and heavy-lift launch capabilities to its customers, as well as small and micro satellite launch capabilities via its Rideshare Program. This balance has worked well over time and could shift a lot as Starship begins to launch more frequently. Something we will have to keep an eye on in the future.
Conclusion
The Falcon Heavy is an interesting rocket that SpaceX has been working on for a while now. The combination of power and reusability makes it unlike a lot of other vehicles within the industry. We will have to wait and see how it progresses and the impact it has on the space industry.